IRA terror suspects, thought to include the alleged killers of Lord Mountbatten and a British ambassador, were secretly given assurances they were safe from prosecution, it has been claimed.

The correspondence published by the 'Sunday Telegraph' suggests Bertie Ahern's Government covertly put in place a scheme promising terrorists they did not face arrest.

Until now, it was thought assurances were given to suspects - known as "on the runs" - only by the British government during peace negotiations.

However, minutes of meetings between senior Irish and British officials suggested the Irish Government was operating an informal scheme with terrorists.

It raises the prospect that IRA terrorists who committed atrocities in the Republic - including the murders of Lord Mountbatten and Christopher Ewart-Biggs, the British ambassador to Ireland - were given assurances that they were not facing arrest.

The disclosure comes days after Prince Charles visited Mullaghmore, the village where his great-uncle Lord Mountbatten was murdered by the IRA.

In a memo written on May 3, 2000, Jonathan Stephens, then associate political director in the UK's Northern Ireland Office, outlined discussions that had taken place at the Irish Embassy in London. He wrote: "On OTRs [on the runs], the British side undertook to operate the Irish procedure of clarifying the position of named individuals and reviewing cases where appropriate, but with no guarantees of the outcome: Sinn Féin want an undertaking that the general principle of not pursuing OTRs will be recognised by July."

Mr Stephens, now permanent secretary at the Northern Ireland Office, added under the subject heading OTRs: "Reflecting earlier discussions in Downing Street, Jonathan Powell [Tony Blair's chief of staff] said we were prepared to operate a similar system to the Irish one. If we were given a list of names, we would clarify with the police and the prosecuting authorities the position of those individuals and, where appropriate, review whether it remained in the public interest to pursue a prosecution."

Senior Irish government officials attended the talks at the embassy, and Sinn Féin was represented by Martin McGuinness and Gerry Adams.

In a second memo, sent to Mr Powell on December 6, 2000, an official in the Northern Ireland Office wrote of continuing discussions about 'on the runs' saying: "The Irish plugged away at their Attorney-General's idea of using the royal prerogative of mercy."

The Department of Justice insisted it never operated an amnesty for criminals wanted for terrorist offences.

"It is not clear what procedure is being referred to but, in any event, it would not have been possible to give anyone assurances that they would not face prosecution for offences in the absence of the introduction of the OTR scheme which had been envisaged but was not proceeded with," a spokesman said.

"There is not, and never has been, in operation here any form of amnesty for persons wanted for the commission of terrorist offences. An Garda Síochána will pursue fully evidence which comes to light in relation to any cases."